The present application relates to the field of materials. More particularly, it relates to a porous, hydrophobic polymethyl-silsesquioxane having remarkable properties of adsorption of organic molecules.
The use in industry of adsorbent materials such as activated carbons, silicas, aluminas or zeolites is known for applications as varied as the purification of water or air to prevent pollution, the separation of liquids or gases by chromatography, the supporting of catalysts or the encapsulation of active substances, to quote just a few examples.
The adsorbent properties of the materials depend on a certain number of physical parameters such as apparent density, specific surface area, particle size, pore volume and pore distribution, indicating their microporosity ( less than 2 nm), their mesoporosity (between 2 nm and 50 nm) or their macroporosity ( greater than 50 nm). A support will also be characterised by its thermal stability, its regenerability, the reversibility of its adsorbent capacities, its hydrophobicity, its inflammability and its absence of toxicity.
At present, the most commonly used hydrophobic adsorbent is activated carbon. However, this has the disadvantage of being inflammable and forming explosive mixtures with air. It is also difficult to regenerate and has a limited adsorption capacity.
Another class of commonly used adsorbents are the silicas. They exist in a wide range of specific surface areas and particle sizes and, as a result, have varying adsorbent properties.
The present application relates to a hydrophobic material which belongs to the family of polymethylsilsesquioxanes, hereinafter abbreviated to PMS, which is thermally stable and has the capacity to adsorb several times its own weight in organic substance.
More precisely, the present application describes a porous polymethylsilsesquioxane in powdered form containing the units 
characterised by a specific surface area between approximately 50 m2/g and 500 m2/g, a pore radius smaller than 1 nm for 90% of the pores, and insolubility in water and organic solvents.
In preferred embodiments, the polymethylsilsesquioxane according to the invention has a pore volume between 0.1 cm3/g and 0.8 cm3/g and/or a monolayer volume between approximately 10 cm3/g and 60 cm3/g.
The polymethylsilsesquioxane according to the invention may also contain the units 
They can be present owing to incomplete polymerisation during the preparation reaction described hereinbelow or owing to treatment which results in partial hydrolysis of the PMS.
The present invention also relates to a process for the preparation of the said polymethylsilsesquioxane.
FIG. 1 is a graph of the differential thermic analysis of a MPMS according to the invention; and
FIG. 2 is a graph of X-ray diffraction spectra for 2 qualities of porous PMS according to the invention.